PHOTO: SHUTTERSTOCK

A few weeks ago, I passed a significant milestone on my journey to becoming a grumpy old man: I yelled at some kids during a movie.

Did I need to ensure that my viewing of “Shazam: Fury of the Gods” was aesthetically pure and unfettered by distraction? No, probably not. But these youths (now that I’m pushing 40, I can only estimate that they were between 15 and … 30) were really pushing it. Phones were out — not for an occasional check or clandestine text but for normal use. The kid nearest me was repeatedly scrolling Instagram, because, apparently, paying $11 for a giant image just isn’t visually stimulating enough. They were chatting; they were fidgeting.

And, in a cardinal sin I’ve noticed far too frequently at the cinema, they had removed their flip-flops and had their bare feet up on the reclining seat. Pure, unshielded toes, mere inches from my popcorn. So I barked. 

Admittedly, I might have simply chosen another seat. But the problem is spreading.

At several regional theater performances — you know, when the actors are physically present and can actually hear you being a clod — I’ve caught people having whole conversations, rooting through purses and even vaping. It’s not a geographical phenomenon; in Manchester, several performances of the musical adaptation of “The Bodyguard” have been halted because patrons refuse to stop belting along with “I Will Always Love You.”

It seems that our grasp of how to behave in public — tenuous in the best of times — was loosened considerably by spending several years on the couch. In the interest of common decency and decorum, let’s review.

At the Movies

There are fewer rules here than in most other communal events, which should make them easy to keep track of; paradoxically, though, the cinema is also the site of frequent disputes over proper behavior. Let’s make it simple: Don’t talk above a whisper, don’t use your phone (besides a quick check) and wear all the clothing you would wear to a restaurant.

While there’s an argument to be made that standards of behavior change generationally — perhaps making something like phone usage more tolerable than it was a decade or two ago — movies take place in a big, dark room that is meant to have moments of quiet. The very architecture is built to remove distractions. If you’re providing some, everyone notices; you may think you’re being sly, but I assure you, 15 people are mad at you, and they’re in the right. You paid good money to be here; get your money’s worth and pay attention.

At the Theater

No talking. Do not, at any point, make use of your vocal cords. At all. “But I was just saying that I’ve seen that actress in …” Well, no, that’s not important. It was not urgent that you share that information. “I was telling my friend that I’m going to the bathroom!” I bet they’ll figure it out. “I couldn’t hear what the actor said, and I was asking my friend to repeat it!” Such is the uncertainty of live theater. I bet you’re bright enough to pick up the thread later.

You’re mere feet from people who are being paid to perform for you and who are trying to pretend you’re not there; don’t be rude. If you’re not capable of going two hours without speaking, hey — the theater’s not for everyone. Guess you’ll have to miss out on cool stuff because you can’t bear the idea of people not focusing on you for a little while.

At a Concert

This one’s controversial. Some folks think that you should watch a concert like you would watch a movie, keeping full focus on the stage. Others feel that a concert is a social occasion for friends to hang out and chatter is expected.

I understand the latter argument in the case of free events and some festival-type environments. But in this era of skyrocketing ticket prices, it strikes me as incredibly rude to try to talk over an experience that your neighbor paid hundreds of dollars for. Most concerts take place in a venue with a bar or other area away from the audience; if you simply must chat, go there. If the people around you are generally looking at the stage, join them.

Oh, and a particularly grumpy word on singing along: When everyone else is singing along, go ahead. If it’s just you, guess what: You can’t sing, and no one wants to hear you.

At a Sporting Event

And last, An environment where it’s generally okay to chat. No one is going to tell you that you can’t converse with your companions at a baseball game; it’s the national pastime, not the national thing-to-focus-on. (Try to avoid the decibel level commonly known as the “drunken yammer,” but other than that, you’re fine.)

Do not, however, look at the game as an opportunity to make yourself the center of attention. Do not try to get the wave going; do not do that “woo” thing that plagued PNC Park for a few years. Do not make obvious jokes at a loud volume or try to yell clever things at the players (you’re in section 316, they cannot hear you). In short: Don’t be a jagoff. And if you don’t know what behavior qualifies as jagoffery … you’re probably a jagoff.